English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Recent photometric results have identified a new population among globularcluster stars. This population, referred to as the ``extended P1'', has beensuggested to be the manifestation of a new abundance pattern where the initialmass fraction of He changes among cluster stars that share the same CNO values.The current paradigm for the formation of the multiple stellar populations inglobular clusters assumes that variations in He are the product of chemical``enrichment'' by the ashes of the CNO-cycle (which changes He and otherelements like C, N and O simultaneously). We obtained MIKE@Magellan spectra ofsix giant stars in NGC 2808, a cluster with one of the strongest examples ofthe extended P1 population. We provide the first complete characterization ofthe light elements abundances for the stars along a significant range of theextended P1 photometric group. The stars from our sample appear to behomogeneous in C, N, O, Na, Mg and Al. The lack of a significant change inthese products of the CNO-cycle, suggest that unlike the rest of thepopulations identified to date, the photometric changes responsible for theextended P1 feature are a consequence of an alternative mechanism. Ourmeasurements, are consistent with the interpretations where the changes of theHe mass fraction among these stars could be consequence of p-p chainnucleosynthesis (which could increase the He in stars without affecting heavierelements). Having said that, direct measurements of He are necessary toconclude if variations of this element are present among extended P1 stars.

Constant light element abundances suggest that the extended P1 in NGC 2808 is not a consequence of CNO-cycle nucleosynthesis